When I started learning C Sharp, I started learning with ASP.Net Core 2.0. I’ll try to mention version numbers.
Language topic
[[Declarations]] - defining variables.
[[Generics]]
[[GetOnly]] function
[[InlineIf]] - an inline if statement, is an if condition inside a statement.
[[Interfaces]]
[[Inheritance]]
[[Linq|Linq|home]] -
[[Mock]] - Mock objects used for setting up applcation testing.
[[Null]] - null topics.
[[Operators]] - used for expressions
[[Scope]] - Scope topics (Public/ Private/ Protected) etc.
[[Tagging]] - Code tagging is when you add flags (for example [Required]) to property, class, or function declarations.
Other topics
[[ASynchronousCRUD]]
[[Automapper]] - A library to map ViewObjects to objects, objects to DataObjects
[[CORS]] - Cross origin scripting.
[[Email]] - there was a change to how you did email between asp.net core 1 and 2, and again in 2 to 3.
Language Evolutions
https://www.dotnetcurry.com/csharp/1286/csharp-7-new-expected-features - Discusses enhancements made with C# 7.0
https://www.dotnetcurry.com/csharp/1489/csharp-8-visual-studio-2019 - Discusses enhancements made with C# 8.0 which was delivered with VS2019